Seattle Mariners acting manager Robby Thompson, who’s in charge as Eric Wedge recovers from a stroke, suffered a quick mental lapse during a ninth inning meltdown that contributed to their epic loss to the Boston Red Sox Thursday night.

Here’s how it went down: Thompson was to pulling Tom Wilhelmsen after he allowed the first four batters in the inning to reach base. He wanted right-hander Yoervis Medina, but he initially raised his left arm, then quickly caught his mistake and began pointing to his right arm.

Too late though, as third base umpire Gary Darling saw the left hand first, and the left-hander also warming up in the bullpen, Oliver Perez, had to come out.

“We wanted to go to Medina there and if we had to go to Ollie, he was the next guy,” Thompson said, via MLB.com . “If there was anything today for me, it was a lesson learned that if you make a motion with either hand, that’s it. I didn’t realize that… I did point to the pen, but I didn’t have time to [tap his other arm] for the right-hander,” Thompson said. “He’d already turned. That’s when I wanted to make sure he knew who I wanted to go to and [crew chief] Gary Darling said it’s too late, you raised your left hand up.”

Perez then proceeded to give up singles to Shane Victorino and Dustin Pedroia. He did strike out David Ortiz, the man they intended to have him face. Then it was time for Thompson’s original choice, Medina, and three batters later, Daniel Nava smacks the walk-off single to win it 8-7.